The most amout of blood you could possibly lose and still survive in a hospital for 2 or 3 days without a transfusion?

Depends. A young person can endure even greater amounts of blood loss without going into hypotensive shock. They may feel light headed and may have orthostatic hypotension.
May be 1-2 liters. An healthy individual can withstand probably upto 1liter rapid loss, but after that it may be difficult. If it is slow bleeding, even if you lose 2-3 liters, the body has time to adjust.
Varies. A healthy person can endure 10-15% blood volume loss before hypotensive shock would threaten them. Someone with severe cardiac disease might not survive lesser amounts of blood loss.